Strengthened transmission tubes for falling film evaporators

ABSTRACT

The present invention discloses strengthened heat transmission tubes for falling film evaporators. The tube includes a tube body of the heat transmission tube and fins disposed on an outside surface of a heat transmission section of the tube body. The fins spirally surround the outside surface of the tube body of the heat transmission tube along an axial direction. The roots of the fins are integrally connected with the tube body. Each of the fins has a cross sectional T shape. Interspaces between two neighboring fins along the axial direction of the tube form small holes for coolants flow and evaporation, and form circular shape channels along the spiral direction. Each T shape fin has fin troughs along peripheral direction. The outer surfaces of the fins are disposed with grooves or extrusion lugs that guide coolants flow. Internal tube body is disposed with internal teeth. The present invention satisfies the characteristics of falling film evaporation, can guide coolant flow, and prevent excessive accumulation of coolants on outer walls of the heat transmission tubes. It also ensures the direction of coolants flow downwards and improves heat transmission efficiency of falling film evaporation.

TECHNICAL FIELD

The present invention relates to the heat transmission tube technology field, especially the strengthened heat transmission tubes in horizontal shell tube type falling film evaporators.

BACKGROUND TECHNOLOGY

Horizontal shell and tube falling film evaporators are increasingly becoming the focus of heat exchanging equipment manufacturers due to their less coolant injection amount and high heat exchange efficiency. The working principles of the falling film evaporators are as follows. Multiple rows of horizontally placed heat transmission tubes are installed within a heat exchanger. Coolants are evenly sprayed from the top of the heat transmitter down to the top level heat transmission tubes and along the lengths of the heat transmission tubes. The coolants then sequentially drip from an upper row of heat transmission tubes onto a lower row of heat transmission tubes. The heat transmission tubes exchange heat with the coolants dripped onto the tubes to ensure that the coolants are evaporated. The heat exchange result of this type of falling film evaporation, on the one hand, depends on whether the heat transmission tubes and the coolants can sufficiently exchange heat and whether there is a sufficient amount of coolants to keep the heat transmission tubes wet; on the other hand, depends on whether the coolants on the outer surfaces of the upper row heat transmission tubes can entirely drip onto the outer surfaces of the lower row of heat transmission tubes. Therefore, the heat transmission tubes in the falling film evaporators play a very important role in ensuring the heat exchange result and improving heat exchange efficiency of falling film evaporation.

The heat transmission tubes with smooth surfaces are no longer adopted by the evaporator and heat exchanger manufactures due to their low heat transmission efficiency, expect for special circumstances. As shown in invention patent ZL200510132040.2 with the title “a type of copper heat exchanging tube for the cooling condensers of the bromine cooling units”, the current strengthened heat transmission tubes are ordinarily added with fins on the outer surfaces of the heat transmission tubes, which increase the heat exchanging areas in order to improve heat transmission efficiency. However, coolants are likely to accumulate between fins of the falling film evaporation heat exchanger to form curved liquid surfaces, which are disadvantageous to the dripping flow of the coolants. At the same time, the surfaces of the fins are smooth, which go against sufficient engagement with the coolants, and they lack the evaporation cores required for evaporation. Thus the heat transmission result is not satisfactory.

Other factories adopted heat transmission tubes such as those shown in invention patent ZL200510134630.9, with the title “a type of full-liquid copper evaporation heat exchanging tube for electricity cooling units”. Although this type of heat transmission tubes can effectively form evaporation cores required for the coolants to evaporate and can improve heat transmission results, this type of heat transmission tubes also have smooth outer surfaces, which go against sufficient exchange with coolants. In addition, this type of heat transmission tubes cannot effectively lead the coolants to sequentially drip downwards row by row, which make the coolants dripping from top to bottom without directions. The falling coolants are likely to go astray or splash and leave the heat transmission tubes, such that they cannot participate in heat exchange, which lead to heat loss and unsatisfactory heat transmission results.

In order to adapt to the special manner of heat transmission in falling film evaporation and improve the head exchange ability of the falling film evaporators, it is necessary to further modify the structure of the heat transmission tubes and improve the heat transmission ability of the heat transmission tubes.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a type of highly efficient strengthened heat transmission tubes specifically adapted for falling film evaporation.

The present invention is achieved by adopting the following schemes. A strengthened heat transmission tube for use in falling film evaporators comprises a tube body of the heat transmission tube and a plurality of fins located on the outer surface of the heat transmission section of the tube body. The fins spirally surround the outside of the tube body along its axial direction. The roots of the fins are integrally connected with the tube body. The fin has a sectional “T” shape along the axial direction. The interspace along the axial direction between two neighboring T-shape fins along axial direction forms small holes for coolants circulation and evaporation. Such interspace also forms circular channels along the spiral direction. The T-shape fins along peripheral direction of the tubes include peripheral fin troughs that cut and divide the fins. The outer surfaces of the fins include grooves or extrusion lugs that guide the coolants flow. The tubes include internal teeth within the tubes.

Along the axial direction, there are 26-60 spiral T-shape fins per inch and their spiral angle is 0.3-2.5°.

There are 60-160 small holes positioned along the peripheral direction of a tube. The distance between the small holes is 0.05-0.5 mm along periphery direction. The height of the small hole is 0.1-0.8 mm.

The rotation direction of the grooves on the outer surface of the fins is the same as the rotation direction of the spiral fins, such that these grooves form circular tunnels along periphery direction. The width of the groove is 0.05-0.5 mm and its depth is 0.02-0.2 mm.

The extrusion lugs on the outer surface of the fins has an angle of 0-80° with the axial direction of the tube body of the heat transmission tubes.

The number of extrusion lugs on an outer surface of each fin is one or above two. The height of the lug is 0.01-0.25 mm. The width of the lug is 0.02-0.4 mm. More than two lugs are parallel to each other. The distance between the lugs is 0.05-0.7 mm.

Two sides of the outer surface of the T-shape fins include edge grooves or chamfers that guide the flow of the coolants.

The internal teeth within the tube bodies are in a screw thread shape. The sectional shape of the screw thread shape internal teeth is close to a triangle shape. The interior angle of the internal teeth is 10-120°.

The range of the angle between the screw thread shape internal teeth and the axial direction of the tube body is 20-70°. There are 6-90 internal teeth. The height of the internal teeth is 0.1-0.6 mm.

The present invention has the following beneficial results. The interspaces among the T-shape fins form many small holes, which provide the evaporation cores when the coolants evaporate, strengthening the evaporation heat exchange. The small holes along the spiral are connected to form circular channels, which are favorable for circular flow of the coolants and strengthen the vapor-liquid phase disturbance during coolants evaporation, and improve the heat exchange results. Using peripheral fin troughs to penetrate and divide the fins on the circular periphery into multiple fins, such that each hole has interspaces in both the axial and peripheral directions, which are favorable for coolants to enter the small holes. This ensures that the coolants are continuously supplied, and the coolants vapor is released during the coolants evaporation. Thus, the evaporation can continue as a continuing process without stop.

The outer surface of the fins of the heat transmission tubes has grooves. These grooves are connected to form circular flow channels along the peripheral direction of the heat transmission tubes. These grooves guide the flow of extra coolants on the outer surfaces of the heat transmission tubes and prevent coolants from accumulating on the outer surfaces of the heat transmission tubes. On the one hand, this prevents thick liquid film forming on the outer surfaces of the tubes, which causes the lower row of the tubes lacking coolants and causes dry evaporation. On the other hand, this prevents coolants from upper rows of tubes dripping onto the thick liquid film, which causes coolants to splash and cannot participate in heat exchange, causing reduced heat transmission efficiency. The circular channels can also ensure the direction of the falling coolants, and prevent the coolants from straying during dripping and prevent the situation where the coolants cannot drip onto the tubes below, causing the lower rows of tubes lacking coolant, resulting in dry evaporation and causing coolants cannot contact with heat transmission tubes such that the efficiency of the evaporator is reduced.

The outer surface of the fins of the heat transmission tubes is disposed with one or more parallel oblique lugs, which can increase the coarse degree of the outer surfaces of the transmission tubes, increase the contact areas between the coolants and heat transmission tubes, ensure the sufficient contact with the coolants and outer surface of the heat transmission tubes, and improve heat exchange efficiency. Such structure can also slow the falling speed of come some of the coolants, ensure sufficient coolants can enter the small holes of the heat transmission tubes, and ensure the formation of continuous evaporation process.

Two edges of each T-shape fins may also be disposed with side grooves or chamfers. On the one hand, this structure can more effectively guide the coolants into the small holes of the heat transmission tubes. On the other hand, this structure can guide extra coolants to drip downward, ensuring direction of the dripping and increasing the heat transmission efficiency.

The internal surfaces of the heat transmission tubes are also disposed with internal teeth in screw thread shapes, which increase the heat transmission areas of the heat transmission tubes, and can strengthen the fluids' turbulent flow and increase heat exchange efficiency within the tubes.

Using the above described structure, the present invention increases the heat exchange efficiency of the internal and outer surfaces of the heat transmission tubes, achieves the optimum combination of heat exchanges efficiencies of internal tubes and outside of the tubes. The present invention improved the overall heat transmission efficiency of the heat transmission tubes and suitable for use in falling film evaporators and other evaporators.

BRIEF DESCRIPTION OF DRAWINGS

The present invention is further described with reference to the following drawings.

FIG. 1 shows a sectional diagram of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 2 shows a three dimensional structural diagram for a part of the heat transmission section of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 3 shows a structural diagram of grooves on the surfaces of the fins of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 4 shows a structural diagram of two extrusion lugs on the surfaces of the fins of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 5 shows a structural diagram of four extrusion lugs on the surfaces of the fins of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 6 shows a structural diagram of side tunnels and chamfers on the surfaces of the fins of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 7 shows a structural diagram of the combination of grooves and extrusion lugs on the surfaces of the fins of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

FIG. 8 shows a structural diagram of the combination of extrusion lugs and side tunnels on the surfaces of the fins of the strengthened heat transmission tube used in falling film evaporators according to the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT

As shown in FIG. 1 or 2, the present invention comprises the tube body 1 of the heat transmission tube and fins 2 disposed on the outer surface of the heat transmission tubes. The fins 2 spirally surrounds the tube body 1 of the heat transmission tube along the tube's axial direction. The roots of the fins 2 are integrally connected with the tube body 1. The fins 2 has a sectional T shape along the axial direction. The interspace along axial direction between two neighboring T-shape fins 2 along axial direction forms small holes 3 for coolants circulation and evaporation. Such interspace also forms circular tunnel along the spiral direction. The T-shape fins 2 along their peripheral direction include peripheral fin troughs 4 that cut and divide the fins. The outer surfaces of the fins include grooves 5 or extrusion lugs 6 that guide the coolants flow. The tubes include internal teeth 7 within the tubes body 1.

Along the axial direction, there are 26-60 spiral T-shape fins 2 per inch and their spiral angle is 0.3-2.5°. The thickness of the material for the T-shape fins is 0.1-0.4 mm.

There are 60-160 small holes 3 positioned along the peripheral direction of a tube. The distance between the small holes 3 is 0.05-0.5 mm along periphery direction. The height of the small hole 3 is 0.1-0.8 mm. The size of the small hole 3 can be adjusted according to the characteristics of different coolants, ensuring evaporation efficiency.

As shown in FIG. 3, the rotation direction of the grooves 5 on the outer surface 21 of the fins 2 is the same as the rotation direction of the spiral fins 2, such that these grooves 5 form circular channels along peripheral direction. The width of the groove 5 is 0.05-0.5 mm and its depth is 0.02-0.2 mm. The grooves 5 may be in an arc shape.

As shown in FIG. 2, or 4 or 5, the extrusion lugs 6 on the outer surface 21 of the fins 2 has an angle of 0-80° with the axial direction of the tube body 1 of the heat transmission tubes.

The number of extrusion lugs 6 on outer surface 21 of each fin 2 is one or above two. The height of the lug 6 is 0.01-0.25 mm. The width of the lug 6 is 0.02-0.4 mm. More than two lugs 6 are parallel to each other. The distance between the lugs 6 is 0.05-0.7 mm.

As shown in FIG. 6, two sides of the outer surface 21 of the T-shape fins 2 include edge grooves 22 or chamfers 41 that guide the flow of the coolants.

As shown in FIG. 7 or 8, grooves 5 and extension lugs 6, extension lugs 6 and edge grooves 22 may have difference combination according to the actual results.

As shown in FIG. 1, the internal teeth 7 within the tube bodies 1 are in screw thread shape. The sectional shape of the screw thread shape internal teeth 7 is close to a triangle shape. The interior angle of the internal teeth is 10-120°.

The range of the angle between the screw thread shape internal teeth 7 and the axial direction of the tube body 1 is 20-70°. There are 6-90 internal teeth 7. The height of the internal teeth 7 is 0.1-0.6 mm.

The present invention's heat transmission tubes may be made by using special machine that is able to integrally process both internal tube and outside of the tube simultaneously. The specific process is as follows. First, a spiral shaped fin 2 is made on the outer surfaces of the tube bodies 1 of the heat transmission tubes. Then, cutting knives are used to cut and divide the spiral shaped fin 2 into multiple fins. Then, rolling and burnishing cutting tools are used to roll and press the fins 2 into T-shape fins. In next step, various corresponding knives are used to press and make grooves 5 or extension lugs 6 on the outer surface 21 of the fins 2. Using rolling press and rotation press processes, one can save the manufacturing cost and increase the strength and heat transmission areas of the heat transmission tubes.

With reference to specific examples, the specific structures of the strengthened heat transmission tube in the falling film evaporators according to the present invention are explained below.

Exemplary Embodiment 1

The outer diameter of the body 1 of the heat transmission tube is 25.32 mm. The tube wall thickness of the heat transmission section is 0.635 mm. The small hole 3 formed by fins 2 has a width of 0.406 mm and a depth of 0.6 mm. There are 150 peripheral fin troughs 4. The width of each peripheral fin trough 4 is 0.1 mm. The outer surfaces 21 of the T-shape fins 2 are processed to form two parallel extrusion lugs 6, the height of which is 0.08 mm and the width of which is 0.2 mm. The inside of the tube body 1 of the transmission tube is also processed to form screw thread shaped screw thread internal teeth 7. There are 52 internal teeth 7 per inch, the height of which is 0.35 mm. The internal teeth form 45° angle with the axis of the tube body 1. The teeth top angle is 30°.

According to actual tests data statistics, in comparison with the prior art, the falling film evaporator of the present invention raised the heat transmission result by 15%, when the coolant R134a was used.

In the examples of the present invention, when the metal materials' heat transmission characteristics and ratio of characteristics versus price are taken into consideration, the heat transmission tube preferably is made of copper material. Copper alloy, aluminum, aluminum alloy, low carbon steel, or copper-aluminum composite material may also be used.

The above is a detailed introduction of the strengthened heat transmission tubes for use in falling film evaporators. The present specification used specific examples to explain the structure and implementation methods of the present invention. The above examples are only to assist in understanding of the methods and their essential characteristics of the present invention. At the same time, to a person of ordinary skill in the art, according to the characteristics of the present invention, the specific implementation manner and scopes of implementation all can be changed. In summary, the content of the present specification should not be understood as limitations to the present invention. 

1. A strengthened heat transmission tube for falling film evaporators, comprising a tube body of the heat transmission tube and a plurality of fins disposed on an outside surface of a heat transmission section of the tube body, the fins spirally surrounding the outside surface of the tube body of the heat transmission tube along an axial direction of the tube, roots of the fins being integrally connected with the tube body; characterized in that: each of the fins has a cross sectional T shape along the axial direction of the tube; interspaces between two neighboring fins along the axial direction of the tube form small holes for coolants flow and evaporation, and form circular shape channels along the spiral direction of the fins; each T shape fin has peripheral fin troughs along peripheral direction of the tube that cut and divide the fin; outer surfaces of the fins are disposed with grooves or extrusion lugs that guide coolants flow; and internal tube body is disposed with internal teeth.
 2. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: along the axial direction, there are 26-60 spiral T-shape fins per inch and their spiral angle is 0.3-2.5°.
 3. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: there are 60-160 said small holes positioned along the peripheral direction of the tube; the distance between two adjacent small holes is 0.05-0.5 mm along peripheral direction; and the height of the small hole is 0.1-0.8 mm.
 4. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: rotation direction of the grooves on the outer surface of the fins is the same as the rotation direction of the spiral fins; said grooves are connected together along the peripheral direction to form circular direction flow channels; the width of the groove is 0.05-0.5 mm; and the depth of the groove is 0.02-0.2 mm.
 5. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: the extrusion lugs on the outer surface of the fins has an angle of 0-80° with the axial direction of the tube body of the heat transmission tubes.
 6. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: the number of extrusion lugs on the outer surface of each fin is one or above two; the height of the lug is 0.01-0.25 mm; the width of the lug is 0.02-0.4 mm; more than two lugs are parallel to each other; and the distance between the lugs is 0.05-0.7 mm.
 7. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: two sides of the outer surface of the T-shape fins include edge grooves or chamfers that guide the flow of the coolants.
 8. The strengthened heat transmission tube for falling film evaporators according to claim 1, characterized in that: the internal teeth within the tube bodies are in a screw thread shape; sectional shape of the screw thread shape internal teeth is close to a triangle shape; an interior angle of the internal teeth is 10-120°.
 9. The strengthened heat transmission tube for falling film evaporators according to claim 8, characterized in that: a range of the angle between the screw thread shape internal teeth and the axial direction of the tube body is 20-70°; there are 6-90 internal teeth; height of the internal teeth is 0.1-0.6 mm. 